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Mathematics 8 Online
OpenStudy (anonymous):

Can somebody help me with this Anti-Derivative problem??

OpenStudy (anonymous):

myininaya (myininaya):

do you know trig substitution?

myininaya (myininaya):

i hope so

OpenStudy (across):

\[\frac{df}{dx}=\frac{3}{\sqrt{1-x^2}}\]\[f\left (\frac{1}{2}\right ) = 8.\] \[df=\frac{3}{\sqrt{1-x^2}}dx\]\[f(x)=3\sin^{-1}(x)+c\]\[8=3\sin^{-1}\left(\frac{1}{2}\right )+c\]\[c=8-3\sin^{-1}\left(\frac{1}{2}\right )\]\[f(x)=\frac{3}{\sqrt{1-x^2}}+8-3\sin^{-1}\left(\frac{1}{2}\right )\]

myininaya (myininaya):

\[\text{ Let } x=\cos(\theta) => dx=-\sin(\theta) d \theta\] \[3\int\limits_{}^{}\frac{1}{\sqrt{1-\cos^2(\theta)}} -\sin(\theta) d \theta=3\int\limits_{}^{}-1 d \theta=-3 \theta+C\]

myininaya (myininaya):

\[=-3\cos^{-1}(x)+C\]

OpenStudy (anonymous):

I didnt know we needed trig substution.. My professor didnt cover this.

myininaya (myininaya):

\[f(x)=-3 \cos^{-1}(x)+C\]

myininaya (myininaya):

there is also a formula you can use

myininaya (myininaya):

i don't do formulas

OpenStudy (anonymous):

Oh ok.. Thank you

OpenStudy (across):

whoops, messed up above xd zzz

myininaya (myininaya):

\[f(\frac{1}{2})=-3\cos^{-1}(\frac{1}{2})+C=8 =>-3 \cdot \frac{\pi}{3}+C=8\] \[C=8+\pi\]

myininaya (myininaya):

\[f(x)=-3 \cos^{-1}(x)+8+\pi\]

OpenStudy (across):

\[f(x)=3\sin^{-1}(x)-3\sin^{-1}\left (\frac{1}{2}\right )+8\]

myininaya (myininaya):

-cos inverse or sin inverse whatever! same thing

OpenStudy (anonymous):

Thank you myininaya! :)

OpenStudy (across):

\[f(x)=-3\cos^{-1}(x)+\pi+8\]

myininaya (myininaya):

i could had made the subsition x=sin(theta) instead and got the sin inverse

myininaya (myininaya):

would you like to see?

OpenStudy (anonymous):

Nah what you have done is good. Thank you!

myininaya (myininaya):

ok have fun

myininaya (myininaya):

oops one more thing when i said thing i mean they just differ by a constant

myininaya (myininaya):

samething*

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